Conversion of 18∶3 Δ9cis, 12cis, 15trans in rat liver microsomes |
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Authors: | Jean-Michel Chardigny Jean-Paul Blond Lionel Bretillon Estelle Mager Didier Poullain Lucy Martine Jean-Michel Vatèle Jean-Pierre Noël Jean-Louis Sébédio |
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Affiliation: | (1) Unité de Nutrition Cellulaire et Métabolique, Université de Bourgogne, Dijon, France;(2) Service des Molécules Marquées, CEA-SACLAY, Gif sur Yvette, France;(3) Laboratoire de Chimie Organique 1, ESCIL, Villeurbanne, France;(4) Unité de Nutrition Lipidique, INRA, 17 rue Sully, BV 1540, 21034 Dijon Cedex, France |
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Abstract: | Several years ago, it was established that the Δ15 trans isomer of α-linolenic acid is converted in vivo into fatty acids containing 20 and 22 carbons (geometrical isomers of eicosapentaenoic and docosahexaenoic acids). The present
study focused on the in vitro Δ6 desaturation, the first step of the biosynthesis of the n-3 long-chain polyunsaturated fatty acids from 18:3n-3. For that
purpose, rat liver microsomes were prepared and incubated with radiolabeled 18∶3 Δ9cis, 12cis, 15cis (18∶3 c,c,c) or 18∶3 Δ9cis, 12cis, 15trans (18∶3c,c,t) under desaturation conditions. The data show that 18∶3c,c,t is converted at a lower rate compared with α-linolenic acid. The product of conversion of 18∶3 c,c,t may be 18∶4 Δ6cis, 9cis, 12cis, 15trans resulting from a Δ6 desaturation of the trans substrate. Moreover, the conversion of radiolabeled 18∶3c,c,t was strongly decreased by the presence of 18∶3c,c,c (up to 48%) while the 18∶3c,c,t only slightly decreased the conversion of radiolabeled 18∶3c,c,c. Thus, the desaturation enzyme presented a higher affinity for the native all-cis n-3 substrate. |
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